Recent revisions

* Decoupled the Perform class into a PerformEngine and a Sequences manager.
* Created a Time util class, used by the PerformEngine in order to avoid WIN32 macro tests
* Some changes in the performance panel
* Commented some classes (need to be continued)

Restructured : BSD/Allman code style, One non-recursive makefile,
Namespace Seq24 and class names begin with a capital letter,
Subdirectories gui, core, utils,
In order to test easier, objects must not build their dependencies, but dependencies must be injected, with the seq24container,
Began to delete unused attributes and methods,
Began to comment with doxygen style.